Why they have different dates?

so this year, mom celebrates Mother's day twice. It was mother's day eve when we arrived in London. I wonder why they set different dates around the world?

So here goes my shout out to mama ;

Happy Mother's Day, Mak!

eventho for me..everyday is your day and you're the person that I can count on no matter what happen.

May you live in prosperity and Allah blessings :')

your apple pie rock my world same goes to your rock bun too.

You're the prettiest person on earth, and papa was lucky to marry you! HAHA

not to forget, you are the most awesome, sporting and coolest person ever, I'm grateful to have you.

p/s she has her on way how to make her children think that we are no good, we will keep learning.